The next generation of magnetic disk data storage media is anticipated to be a patterned magnetic hit data storage media. In current storage media, the magnetic domains used to store data are formed by a recording head. As illustrated in FIG. 1, the conventional data storage media 100, which is in a form of a disk, comprises a base 102, a storage layer 104, and a protective layer 106. As known in the art, the media 100 may be dual sided. But for the purposes of clarity and simplicity, only the upper portion of the media 100 is shown. Within the storage layer 104, there may be a plurality of active regions 104a for storing the data bits and inactive regions 104b isolating each active region 104a. 
In the conventional data storage media 100, the active regions 104a may be formed by the recording head 110 as it flies over the media 100. The recording head 110 may also record the data. The recording head 110 may comprise a permeable core 112 and drive coil 114. During the data recording process, the recording head 110 selects active regions 104a where data bits can be recorded. At the same time, the recording head 110 exerts magnetic field to a large number of grains in the active regions 104a to orient the magnetic moments of the grains in particular orientations. By orienting the magnetic moments in particular orientations, the recording head 110 records the data bits. To read the data bits, there may be a reading head (not shown) near the recording head 110 that can detect the external magnetic field due to remanent magnetization of the individual data bits.
In the patterned magnetic bit storage media, the active regions are not formed by the recording head. In addition, the active regions are not formed during the data write process. Instead, the active regions are formed during manufacturing of the media. Referring to FIG. 2, there is shown a conventional patterned magnetic bit storage media 200. The patterned magnetic bit storage media 200 may comprise a base 202. The base 202 may comprise, among others, a support 202a, a magnetically soft underlayer 202b, and a separator 202c. Above the base 202, there may be a data storage layer 204. A protective layer 206 may be disposed above the data storage layer 204.
In the storage layer 204, there may be a plurality of active regions 204a where data bits can be stored. In addition, there may be a plurality of inactive regions 204b isolating the active regions 204a. Each region 204a may store a single data bit represented by the magnetic moment oriented in a particular orientation. The material in each active region 204a may be a ferromagnetic material exhibiting magnetic field. Meanwhile, the material in the inactive regions 204b may be that which have low permeability and remanence exhibiting low external magnetic field. As such, active regions 204a are clearly defined by the external magnetic field.
The data bit may be recorded in each active region 204a by the recording head 210. The recording head 210 may comprise a permeable core 212 and drive coil 214. To record data bits, the recording head 210 exerts magnetic field onto the each active region 204a and orient the magnetic moments 205 in each active region 204a in a particular orientation. To read data, a separate recording head (not shown) may detect the orientation of the magnetic moments 205. The patterned magnetic bit data storage media described above is anticipated to hold much more data, beyond that is achievable by the conventional data storage media 100 shown in FIG. 1.
Referring to FIG. 3a-3f, there are shown a method of manufacturing the conventional patterned magnetic storage media 200. As noted above, the active regions 204a, which can store the data bits, are formed prior to the data recording process. The media 200 may comprise, among others, a base 202 and a data storage layer 204. The material contained in the data storage layer 204 may be a ferromagnetic material.
To form the patterned media 200, a patterning process is performed. In this process, a layer of resist 208 is deposited on the data storage layer 204 (FIG. 3a). Thereafter, the resist layer 208 may be patterned using a known lithographic process to expose portions of the data storage layer 204 (FIG. 3b). Examples of the known lithographic process may include photolithography process, nanoimprint lithography process, and direct write electron beam lithography process.
After performing the patterning process, the data storage layer 204 is etched using, for example, ion milling process. In this process, the exposed portions of the magnetic data storage layer 204 are etched and removed by reactive ions 222 (FIG. 3c). The resulting media 200 may comprise columns 204a of ferromagnetic material spaced apart and isolated from each other by gaps. The columns 204a may ultimately form the active regions 204a. The gaps are then filled with non-magnetic material with low permeability and remanence to form the inactive regions 204b (FIG. 3d). Thereafter, the media 200 is planarized (FIG. 3e), and a protective coating 206 is deposited (FIG. 3f). The resulting structure may comprise active regions 204a isolated by non-magnetic, inactive regions 204b. 
Some in data storage industry believe that the above method is inefficient and proposed more efficient methods. One of the proposed method incorporates an ion implantation process. Referring to FIG. 4a-4e, there is shown a method of forming the patterned magnetic bit storage media 200 incorporating the ion implantation process.
In this process, the layer of resist 208 is deposited on the data storage layer 304 (FIG. 4a). The material in the data storage layer 304 may be ferromagnetic material. After depositing the resist layer 208, it is patterned using the known lithographic process, and portions of the data storage layer 304 are exposed (FIG. 4b). After the patterning process, ions 322 are implanted into the exposed regions 304b of the data storage layer 304. Instead of removing the material in the exposed regions 304b, the ions 322 are implanted and remain in the exposed regions 304b. The implanted ions 322 may then convert the material in the implanted regions 304d from ferromagnetic at to a paramagnetic material with low permeability and ideally no remanence (FIG. 4c). Hence, inactive regions 304b may form. Meanwhile, the material in unexposed region 204a may remain ferromagnetic as it is not implanted with the ions 322. As a result, the data storage layer 304 comprising active regions 204a and inactive regions 304b substantially isolating the active regions 204a may form. After forming the active and inactive regions 204a and 304b, the remaining resist layer 208 is removed, and a protective layer 206 is deposited on the storage layer 304 (FIG. 4c).
Various approaches may be taken to form the inactive regions 304b. In one approach, the inactive regions 304b are formed by implanting diluting ions 322 with non-magnetic properties into the ferromagnetic material in the exposed regions 304b. In this approach, the ferromagnetic material in the exposed regions 304b is implanted with diluting ions 322 with sufficient dose such that Curie temperature of the resulting material is reduced to room temperature and no longer magnetic at room temperature. To achieve sufficient dilution, atomic concentration of ˜10% or more of the diluting ions 322 may be needed. For a media 200 comprising cobalt (Co) based data storage layer 304 having 30 nm thickness, a 10% concentration implies an ion dose of approximately 3×1016/cm2. This dose may be proportional to the thickness of the storage layer 204 and thus may be less if the data storage layer 204 is thinner.
In another approach, the magnetic material may be converted by affecting the crystallinity or microstructure of the material in the exposed regions 304b. As known in the art, ion implantation process is an energetic process that can cause many atomic collisions. During implantation, the material in the exposed regions 304b, otherwise crystalline and exhibit external magnetic field, may become amorphous and/or disordered. As a result, the material exhibit low ferromagnetism. Meanwhile, the unexposed portion 204a next to the exposed portion 204b may retain its original magnetic properties.
Typical ion dose necessary to amorphize/disorder a silicon substrate is 1×1015 ions/cm2 or higher. In a metal substrate, this required dose may be even higher, particularly if the implant is performed at a room temperature or higher. This method is particularly effective if the original ferromagnetic layer is a multilayer that derives its magnetic properties from the interaction of very thin layers in a stack.
The above proposed methods, although useful, have several drawbacks. For example, the methods may have low throughput. Each method noted above requires ion dose ranging about 1×1016-1×1017 ions/cm2. However, the beam current in a conventional ion implanter is limited due system limitations in generating ions or in cooling the substrate. Accordingly, such a high dose will limit the throughput and increase the manufacturing costs. In addition, the resist used in the process may not survive ion implantation in such a high dose.
In some cases, electron beam is used to directly write or pattern the resist 208. The direct write process may enable much greater resolution. Because this process is a bit by bit process, it is not suitable for high throughput production. The nano-imprint lithographic process, an alternative to the direct e-beam patterning process, however, limits the maximum practical step height of the resist to about 50 nm. Sputtering caused by the ion beam can significantly reduce the thickness of the resist and will limit its ability to shield the layers underneath.
In addition to the resist, the material in the data storage layer may be sputtered. The sputtering may be problematic as the ion dose required is high. The resulting storage layer may be non-planar, having steps with different height. Such a non-planarity may be undesirable as read/write head may be damaged by a rough, non-planar surface. These sputtering effects, whether of the resist or the data storage layer, proceed in proportion to the total dose needed for the process.
Accordingly, a new method is needed.